Figure 24 - Baseline over-exposed picture of two magnets with no color filter. Figure #24 is a baseline photograph without a filter. Because the filters will attenuate the incandescent light source, the photograph is a bit over-exposed. The red, green, and blue channels of the photograph are shown adjacent to the original image and have not been rescaled. For example, the red layer of Figure #24 is saturated with red light.
Using two magnets of the nine magnets seen in Figure #12, in a plastic jig as a test subject, which is providing the applied magnetic filed. One magnet has the north pole and the other magnet has a south pole aligned with the ferrofluid cell. In Figure #24, the light is coming from the direction of the bottom of the photograph and the hysteresis pattern on the lower 1/2 of the page is closer to the light source than the hysteresis pattern on the upper 1/2 of the page.
Note in Figure #24 that we have a glass flaw on the glass surface which is casting a shadow. I find that these shadows are good at providing standardized readings, defining the light level at the center of the shadow as the baseline.

Figure 25 - Spectrograph readings of the red filter with the ferrofluid cell.

In Figure #25, I am showing the spectrum results of the 'red' filter. The black line is the reflection profile of the ferrofluid cell without an applied magnetic field. The magenta line of the graph shows the reflection profile of having a red hysteresis line under the fiber optic probe and the cyan line shows the reflection profile of having a white line, or the eye brow feature. These alignments of the fiber optic probe with the image features are best effort and probable need to be repeated in a few more experiments.